Fix encode to json ignoring driver.Valuer

https://github.com/jackc/pgx/issues/1430

extended_query_builder.go

@@ -1,6 +1,7 @@
 package pgx
 
 import (
+	"database/sql/driver"
 	"fmt"
 
 	"github.com/jackc/pgx/v5/internal/anynil"
@@ -181,6 +182,19 @@ func (eqb *ExtendedQueryBuilder) appendParamsForQueryExecModeExec(m *pgtype.Map,
 					}
 				}
 			}
+			if !ok {
+				var dv driver.Valuer
+				if dv, ok = arg.(driver.Valuer); ok {
+					v, err := dv.Value()
+					if err != nil {
+						return err
+					}
+					dt, ok = m.TypeForValue(v)
+					if ok {
+						arg = v
+					}
+				}
+			}
 			if !ok {
 				var str fmt.Stringer
 				if str, ok = arg.(fmt.Stringer); ok {